Amino acid metabolism in helminths

Metabolism of amino acids is better known in nematodes than in other helminths, particularly in parasites of mammals and humans. There are differences between species and also life-cycle stages, so that the presence of genes encoding the proteins does not ensure functional enzymes, e.g. there are differences in expression of glutamate synthase, arginine decarboxylase and 1-piperideine-carboxylate reductase between the two closely related species or life-cycle stages of sheep abomasal nematode parasites. The main differences in metabolism of amino acids from that in other animals are in properties of individual enzymes, rather than the absence or presence of pathways. Unusual features are the lack a full ornithine-urea cycle in many helminths, the presence of creatinase activity, synthesis of polyamines from either ornithine or agmatine and incorporation of ammonia into glutamate.